The report flagged up an incident where one guard accidently fired his gun into a mirror in a public lavatory while practicing pulling it out of its holster.

On another occasion, a security officer did not notice that he had sent a baby through an X-ray machine.

The Senate Homeland Security Committee is due to hold a hearing into failings at the agency.

The committee chairman, Senator Joe Lieberman, said that eight years after the 9/11 attacks, it was "simply unacceptable" that federal employees and visitors remained exposed to potential terrorist attacks.